1. Field of the Invention
This invention relates generally to diaphram valves for controlling flow of various fluids.
2. Prior Art
Previous designs of control devices operated by a pressure differential have generally involved mechanisms that include a rubber or elstomeric diaphram that is stretched to open, relying, at least in part, on the tensile strength of the elastomer in conjunction with a pressure differential to return the valve to the closed position. Examples of several of these types of valves are shown in patents by: Rich, U.S. Pat. No. 2,877,971; Bryant, U.S. Pat. No. 2,353,143; and Davis, U.S. Pat. No. 2,677,930. Such reliance on elastomer tensile strength has certain inherent design deficiencies that the present invention, by utilizing a flexing diaphram with fabric reinforcement to provide high tensile strength rather than a stretching, purely elastomer diaphram, improves upon. These deficiencies are: (1) diaphram travel or degree of opening is limited by the tensile strength of the elastomer material; (2) diaphram tensile strength and stretching characteristics are adversely affected by temperature from ambient and fluid expansion that are associated with pressure reduction; (3) diaphram travel (valve opening) must be limited to avoid instability, fluttering, or chattering, resulting in a need for large throttling area to achieve acceptable capacity; (4) the diaphram must be fairly thick to provide durability and strength for a throttling operation and to avoid wear failure due to the presence of abrasive materials in the fluid stream, which durability requirements results in the need for greater minimum pressure differential to open such diaphram valve; (5) the tendency of the elastomer material to "take a set", failing to return to its original shape, increases with elastomer thickness resulting in a sluggish operation at lower temperatures. In summary, it is difficult to design an elastomer diaphram that will meet the conflicting requirements of durability, stretchability, stability, and acceptable minimum pressure differential for opening.
Where flow control devices have not utilized a stretchable diaphram element such have taught other closure arrangements. For example, patents by: Randall, et al., U.S. Pat. No. 3,020,925; Spence, U.S. Pat. No. 2,860,657; Zadoo, U.S. Pat. No. 3,792,713; and Johnson, et al., U.S. Pat. No. 3,064,675, show valves that involve an orifice and valve plug arrangement connected to a diaphram and are closed, generally, by a spring arrangement.
Unlike earlier devices, the present invention is directed towards a regulator that utilizes a molded fabric reinforced elastomeric diaphram with high tensile strength that is flexible but does not stretch, and so does not suffer from the inherent problems of such stretchable diaphrams, but is functionally similar thereto.